This invention relates to the microelectronics field in which high-speed, high-accuracy parallel operations are performed in a time-series manner, using pulse modulation signals, to realize intelligent processing equivalent to the human brain.
With the development of microelectronics, an apparatus has been realized, which can process a great amount of information, i.e. can perform intelligent processing or image signal processing. In such an apparatus, multi-bit numeric value information is processed using, in general, binary digital signals. Since, however, the energy consumed in a digital circuit is proportional to the number of pulses used therein, high energy is required for one operation if multi-bit numeric value information is represented by a plurality of pulses. Further, since the signal processing is performed on a sequential basis, a large-scale circuit is required to process a plurality of signals in a parallel manner. To avoid this, processing of multi-bit numeric information using a PWM (Pulse Width Modulation) signal in place of a binary digital signal is now proposed.
The PWM signal has a voltage amplitude which can be represented by a digital value, and a pulse width which indicates analog information. With the development of the microelectronics techniques, a MOS transistor, which is a basic structural element of an integrated circuit capable of processing the PWM signal, has been refined. As a result, a CMOS circuit capable of processing a pulse width at a time resolution of 1 ns has been realized. Parallel sum-of-product calculation which is considered basic intelligent processing can be made efficient, using the PWM signal in a very large-scale, high-speed integrated circuit such as the CMOS circuit.
An arithmetic operation of each pulse of a PWM signal, which indicates multi-bit numeric information, requires a period of time substantially equal to its pulse width. Supposing, for example, that the time resolution is 1 ns in the case of 16 bits, the time required for processing a maximum pulse width indicative of 16 bits is 2.sup.16 ns, i.e. about 70 .mu.s, which is longer by thousand times than the time required for processing a usual digital signal. This being so, it is indispensable to increase the operation accuracy and speed of the multi-bit PWM signal operation circuit.